Add RAM1 configuration in mbed_config.tmpl

[rajkan01]

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The existing "mbed_config.tmpl" is only generating MBED_RAM_START and MBED_RAM_SIZE and not generating MBED_RAM1_START and MBED_RAM1_SIZE, but most of the targets in targets.json has both RAM and RAM1 configuration.
This is a feature request to generate RAM1 configuration if the targets have a configuration in targets.json